1. Field of the Invention
The present invention relates to a plasma display panel. More specifically, the present invention relates to a plasma display panel having improved transparent electrode layer and bus electrode layer structures.
2. Description of the Related Art
In general, a plasma display panel (PDP) is a display device in which ultraviolet rays generated by gas discharge excite phosphors to produce an image and has an advantage of its large screen with thin depth and high resolution over a cathode ray tube. At its essence, a PDP is a matrix of tiny fluorescent lamp pixels which are controlled using electronic drivers in a complex electronic driving scheme.
In a typical alternating current PDP, discharge cells are defined by barrier ribs placed between a front substrate and a rear substrate. Corresponding to each discharge cell, address electrodes are formed on the rear substrate, and display electrodes comprising sustain electrodes and scan electrodes are formed on the front substrate. The address electrodes and the display electrodes are covered with a respective dielectric layer. Each discharge cell has a phosphor layer that emits one of red, blue or green visible light when exposed to ultraviolet light and is filled with a discharge gas (generally a gas mixture of Ne—Xe). Each pixel of the PDP is formed by three adjacent ultraviolet light emitting discharge cells. The ultraviolet light is converted into visible light by the phosphors in each of the three adjacent discharge cells to produce each of the three primary colors, red, blue or green, in varying degrees in the respective discharge cells to produce a specific color in the pixel. The amount of visible light produced in each discharge cell depends on the level of ultraviolet light generated in each discharge cell by the electronic drivers.
In such a PDP, a discharge cell for light emission is selected by the address discharge that occurs by an address voltage applied between the address electrode and the scan electrode. Then, a plasma discharge takes place inside the selected discharge cell by a sustain voltage (Vs) applied between the sustain electrode and the scan electrode, and the plasma emits vacuum ultraviolet rays that excite the phosphor layer in the discharge cell to emit visible light.
For the operation of the PDP, the sustain electrode and the scan electrode are made of a transparent electrode layer such as indium-tin oxide (ITO) so that both the electrodes can transmit the visible light generated inside the discharge cell. The conductance of each transparent electrode layer is compensated by a bus electrode layer made of a metallic material such as silver. The bus electrode layer having a uniform line-width is formed in stripe-pattern on one side of the transparent electrode layer.
The transparent electrode may be formed by (1) forming an ITO layer on the entire front substrate, (2) forming a mask layer on the ITO layer by a well known photolithography process, (3) etching the unmasked ITO layer and (4) stripping the mask layer and cleaning/drying.
The transparent electrode layer of early PDPs was formed in a stripe pattern, and characteristics of discharging in the discharge cell were influenced by only the line-width and the discharge gap thereof. In order to improve discharge efficiency, however, a new structure has recently been introduced in which the line-width of the transparent electrode layer is reduced in the non-discharge region between the discharge cells and in the area contributing substantially little to the sustain discharge, i.e., the area corresponding to outer portions of the discharge cell. This type of transparent electrode layer, however, is susceptible to breakage at locations where there is a small line-width, due to a variety of factors, including poor bonding between the ITO layer and the mask layer, bubbles trapped in the mask layer and excessive etching in the patterning process of the ITO layer. Such breakage of the transparent electrode layer results in a defective discharge cell where the expected discharge does not and cannot occur.
In the event that a transparent electrode layer is broken during the forming process of the display electrode, it is possible to manually repair the breakage by applying the same material as the bus electrode layer on the broken area. However, such repairing requires an additional repairing process while increasing manufacturing cost and lowering productivity.